FRDM-KW40Z datasheet(13/37 Pages) FREESCALE

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FRDM-KW40Z Freescale Freedom Development Board User’s Guide, Rev. 2, 10/2015

Freescale Semiconductor, Inc.

FRDM-KW40Z development board

The external 50 (balanced):100 (unbalanced) balun connects a single-ended 50-Ohm port to the

differential RF port of the MKW40Z SoC transceiver. The layout has a provision for out-of-band signal

suppression (components L4 and C33), if required. The following figure shows the typical topology of the

RF circuitry. The RF connector J5 is provided for conducted measurement purposes, and it is used as DNP.

Figure 7. FRDM-KW40Z board’s RF circuitry

4.2.2

Clocks

The FRDM-KW40Z board provides two clocks:

•

32 MHz Reference Oscillator—Figure 8 shows the 32 MHz external crystal Y1. This mounted

crystal meets the specifications outlined in Reference Oscillator Crystal Requirements for the

MC1320x, MC1321x, MC1322x, and MC1323x IEEE 802.15.4 Devices (document AN3251).

The IEEE Std. 802.15.4 requires the frequency to be accurate to less than 40 ppm.

— Capacitors C41 and C42 provide the bulk of the crystal load capacitance. At 25 °C, the

frequency must be accurate to 10 ppm (or less) to enable temperature variation.

— To measure the 32 MHz oscillator frequency, program the CLKOUT (PTB0) signal to provide

buffered output clock signal.

•

Optional 32.768 kHz Crystal Oscillator—a secondary 32.768 kHz crystal Y2 is provided

(see Figure 9). Use this oscillator for a low-power accurate time base.

— The module provides the Y2 crystal and its load capacitors C46 and C47.

— Load capacitors C46 and C47 provide the entire crystal load capacitance; there is no on-board

trim capacitance.

— The 32 kHz oscillator components are supplied, but not enabled. The 0 Ohm resistors R71 and

R76 disable the 32 kHz oscillator.

FRDM-KW40Z Datasheet(PDF) 13 Page - Freescale Semiconductor, Inc